In the final stages of dehydration the body shrinks, robbing youth from the young as the skin puckers, eyes recede into orbits, and the tongue swells and cracks. Brain cells shrivel and muscles seize. The kidneys shut down. Blood volume drops, triggering hypovolemic shock, with its attendant respiratory and cardiac failures. These combined assaults disrupt the chemical and electrical pathways of the body until all systems cascade toward death.

Such is also the path of a dying species. Beyond a critical point, the collective body of a unique kind of mammal or bird or amphibian or tree cannot be salvaged, no matter the first aid rendered. Too few individuals spread too far apart, or too genetically weakened, are susceptible to even small natural disasters: a passing thunderstorm; an unexpected freeze; drought. At fewer than 50 members, populations experience increasingly random fluctuations until a kind of fatal arrhythmia takes hold. Eventually, an entire genetic legacy, born in the beginnings of life on earth, is removed from the future...

... as harmful as our forebears may have been, nothing compares to what's under way today. Throughout the 20th century the causes of extinction - habitat degradation, overexploitation, agricultural monocultures, human-borne invasive species, human-induced climate-change - increased exponentially, until now in the 21st century the rate is nothing short of explosive. The World Conservation Union's Red List - a database measuring the global status of Earth's 1.5 million scientifically named species - tells a haunting tale of unchecked, unaddressed, and accelerating biocide...

In a staggering forecast, Wilson predicts that our present course will lead to the extinction of half of all plant and animal species by 2100.

You probably had no idea. Few do. A poll by the American Museum of Natural History finds that seven in 10 biologists believe that mass extinction poses a colossal threat to human existence, a more serious environmental problem than even its contributor, global warming; and that the dangers of mass extinction are woefully underestimated by almost everyone outside science. In the 200 years since French naturalist Georges Cuvier first floated the concept of extinction, after examining fossil bones and concluding "the existence of a world previous to ours, destroyed by some sort of catastrophe", we have only slowly recognised and attempted to correct our own catastrophic behaviour. Julia Whitty | Animal Extinction - the greatest threat to mankind.